Although various biped, quadruped and other robots have been proposed as legged mobile robots in recent years, it has been proposed regarding the quadruped robot to provide a curved surface joining a flat surface formed on the rump-like region of the body and the belly-like region, shape the flat surface so that the body actively tilts toward the belly-like region under the robot's own weight with the curved surface being brought into contact with the ground, thereby enabling posture displacement to be performed naturally and more smoothly (see Patent Reference 1, for example).
Patent Reference 1: Japanese Laid-open Patent Application 2003-71753